Shared Contact Structure and Methods for Forming the Same

ABSTRACT

A butted contact structure is provided. In one embodiment, a structure includes a first transistor on a substrate, the first transistor comprising a first source or drain region, a first gate, and a first gate spacer being disposed between the first gate and the first source or drain region. The structure includes a second transistor on the substrate, the second transistor comprising a second source or drain region, a second gate, and a second gate spacer being disposed between the second gate and the second source or drain region. The structure includes a butted contact disposed above and extending from the first source or drain region to at least one of the first or second gate, a portion of the first gate spacer extending a distance into the butted contact to separate a first bottom surface of the butted contact from a second bottom surface of the butted contact.

PRIORITY

This application is a divisional of Ser. No. 16/032,390, filed on Jul.11, 2018, entitled “Shared Contact Structure and Methods for Forming theSame,” which application is incorporated by reference herein in itsentirety.

BACKGROUND

Contacts are typically vertical metal interconnect structures formed inan integrated circuit that connect various components (e.g., the activeregions and gate electrodes) of a semiconductor device to a metal layerof interconnect. Individual semiconductor devices formed in asemiconductor substrate are electrically coupled to each other throughcontacts in order to form functional integrated circuits. As thesemiconductor industry has progressed into nanometer technology processnodes, such as 5 nm nodes, in pursuit of higher device density, newchallenges are presented. Therefore, there is a need for improvedcontact structures and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A depicts a schematic circuit diagram according to someembodiments.

FIG. 1B depicts a top view of an IC layout corresponding to a portion ofthe circuit diagram shown in FIG. 1A.

FIG. 2 depicts a semiconductor device that can be used in forming aportion of the circuit diagram of FIG. 1A according to some embodiments.

FIGS. 3 to 16, 17A, and 17B are schematic cross-sectional views of aportion of the semiconductor device corresponding to various stages offabrication according to some embodiments.

FIG. 18 depicts a portion of the cross-sectional view of FIG. 17A tofurther illustrate additional details in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Various embodiments described below provide methods for forming a sharedcontact structure that enables connection of a source or drain region ofa transistor to a gate of the same or another transistor on a substratewithout the use of a horizontal metal interconnect layer. A tapered gatespacer is disposed laterally between the source or drain region and thegate. The tapered gate spacer extends a distance into a bottom of theshared contact structure between interior angled sidewalls of the sharedcontact structure. The tapered gate spacer and angled sidewalls canensure good metal-fill capability for the subsequent deposited metalfill without voids or seams. The shared contact structure can be formedby a double patterning process using two separate photomasks, each witha portion of a pattern corresponding to the shared contact structure.

The foregoing broadly outlines some aspects of embodiments described inthis disclosure. It is contemplated that the concepts of the presentdisclosure may be implemented for a planar transistor device or for athree-dimensional transistor device, such as the semiconductor device240 described in this disclosure. Some example devices for which aspectsdescribed herein may be implemented include fin field effect transistors(FinFETs), Horizontal Gate All Around (HGAA) FETs, Vertical Gate AllAround (VGAA) FETs, nanowire channel FETs, strained-semiconductordevices, silicon-on-insulator (SOI) devices, or other devices that canbe benefit from aspects of the present disclosure.

FIG. 1A depicts an example of a schematic circuit diagram of a 6T (6transistors) static random access memory (SRAM) cell 100 according tosome embodiments. The 6T SRAM cell 100 includes a first inverter 140that is cross coupled with a second inverter 142. The first inverter 140includes a pull-up transistor 112 and a pull-down transistor 114. Thesecond inverter 142 includes a pull-up transistor 116 and a pull-downtransistor 118. The SRAM cell 100 also includes pass gate transistors110, 120. Gates (e.g., gate 101) of the pass gate transistors 110, 120are coupled to and controlled by a word line WL, and source/drain of thepass gate transistors 110, 120 are coupled to a bit line BL andcomplementary bit line BLB, respectively.

Shared contacts or so-called butted contacts can be used on variousconnections in the circuit diagram shown in FIG. 1A. For example, theconnection between the source/drain region 104 of the pull-up transistor112 and gate 106 of the pull-up and pull-down transistors 116 and 118,and the connection between the source/drain region 115 of the pull-uptransistor 116 and gate 121 of the pull-up and pull-down transistors 112and 114. Other connections can be formed of butted contacts.

FIG. 1B depicts a top view of an integrated circuit (IC) layout 150corresponding to a portion of SRAM cell 100 shown in FIG. 1A. The IClayout 150 includes two pull-up transistors 112 and 116. For clarity,the pull-up transistor 112 is represented by features with a dotted linewhile the pull-up transistor 116 is represented by features with a solidline. The pull-up transistor 112 includes a gate 152 formed over aportion of an active region 154, while the pull-up transistor 116includes a gate 153 formed over a portion of an active region 155. Thegates 152 and 153 may include a metal-containing material, such asdescribed below. Each pull-up transistor (112, 116) includes a drainregion 156, 157 located within the active region 154 and 155,respectively. A butted contact 158, 159 may extend along a length from afirst end to a second end. For example, the first end of the buttedcontact 158 may be in contact with the gate 152 that corresponds to thepull-up transistor 112 within a first inverter (e.g., the first inverter140 of FIG. 1A). The second end of the butted contact 158 is in contactwith the drain region 157 that corresponds to the pull-up transistor 116within the second inverter (e.g., the second inverter 142 of FIG. 1A).Therefore, the butted contact connects the gate of transistors withinone inverter to the source/drain of transistors within a cross-coupledinverter, as shown in the SRAM cell 100. The IC layout 150 also includescontacts 160 and 162. Contacts 160 and 162 can be any suitableinterconnect or contact features desired in the semiconductor device240. For example, contacts 160 and 162 may be disposed on the activeregions 154, 155, respectively, and can be configured to provide avoltage Vcc to source terminals of the pull-up transistors 112 and 116,respectively.

It is contemplated that the transistors and the contact featuresdepicted in FIG. 1B are for illustrative purposes and should not beconsidered as a limitation. The arrangement and/or the number of thetransistors and contact features may vary depending upon theapplication. Other applications for shared or butted contacts includeother memory applications, power devices, and any other semiconductorswhere adjacent components may be connected electrically at thetransistor level. For example, while the present disclosure discusses agate to drain butted contact, other butted contacts may be envisionedsuch as source to drain of adjacent transistors, gate to source ofadjacent transistors, source to body, drain to body, and others.

Some embodiments use a multiple-patterning technology, for example, adouble patterning process, to form butted contacts. For example, arectangular-shape pattern corresponding to the butted contact (e.g.,butted contact 158 of FIG. 1B) may be split or divided into twosquare-shape patterns 158A and 158B. The two square-shape patterns 158A,158B are then recombined using two separate photomasks in successivelithography and etch steps to form a rectangular-shape butted contact158 which is to be transferred to a layer of a device. Since thesquare-shape patterns 158A and 158B are transferred into the layer ofthe device by two separate lithography processes, proper criticaldimension uniformity can be obtained. By breaking a layout into twodifferent photomasks, a minimum line spacing in the combined pattern canbe reduced while maintaining good resolution. In some embodiments, eachphotomask may also include patterns of the nominal contacts to betransferred to the substrate to ensure minimum number of the photomaskinvolved. For example, the first photomask may include a square-shapepattern 158A of the butted contact 158, a square-shape pattern 159A ofthe butted contact 159, and a contact pattern 162A to be formed on theactive region 155, while the second photomask may include a square-shapepattern 158B of the butted contact 158, a square-shape pattern 159B ofthe butted contact 159, and a contact pattern 160A to be formed on theactive region 154. Various embodiments of forming the butted contactswill be discussed in more detail below.

FIG. 2 depicts a semiconductor device 240 that can be used in forming aportion of the SRAM cell 100 of FIG. 1A, for example butted contactswhich provide connections between gate 106 of the transistors 116 and118 and a drain 104 of the transistor 112, or connections between gate121 of the transistors 112, 114 and drain 115 of the transistor 116. Thesemiconductor device 240 has a fin 274 formed on a semiconductorsubstrate 270. The semiconductor substrate 270 may be or include a bulksemiconductor substrate, a semiconductor-on-insulator (SOI) substrate,or the like, which may be doped (e.g., with a p-type or an n-typedopant) or undoped. In some embodiments, the semiconductor material ofthe semiconductor substrate 270 may include an elemental semiconductorincluding silicon (Si) or germanium (Ge); a compound semiconductor; analloy semiconductor; or a combination thereof. The fin 274 provides anactive area of one or more of the transistors of the SRAM cell 100. Thefin 274 is fabricated using suitable processes performed on thesemiconductor substrate 270, including masking, photolithography, and/oretch processes, to form trenches 253 into the substrate 270, leaving thefin 274 extended upwardly from the substrate 270. The trenches 253 maythen be filled with an insulating material such as an oxide (e.g.,silicon oxide), a nitride, the like, or a combination thereof. Theinsulating material may be recessed, such as by using an acceptable etchprocess, to form the isolation regions 278. The insulating material isrecessed such that the fin 274 protrudes above and from betweenneighboring isolation regions 278.

The semiconductor device 240 has gate structures 251 formed over topsurface of the fin 274. As described herein, the gate structures 251 aredummy gate stacks in a replacement gate process, although other examplescontemplate implementing a gate-first process. The gate structures 251are over and extend perpendicularly to the fin 274. Each gate structure251 includes an interfacial dielectric 280, a dummy gate 282 over theinterfacial dielectric 280, and a mask 284 over the dummy gate 282, asshown in FIG. 2. The interfacial dielectrics 280, the dummy gates 282,and the masks 284 for the gate structures 251 may be formed bysequentially forming respective layers, and then patterning those layersinto the gate structures 251. For example, the interfacial dielectrics280 may include or be silicon oxide, silicon nitride, the like, ormultilayers thereof. The dummy gates 282 may include or be silicon(e.g., polysilicon) or another material. The masks 284 may include or besilicon nitride, silicon oxynitride, silicon carbon nitride, the like,or a combination thereof. The layers can be formed or deposited by anysuitable deposition technique. The layers for the interfacialdielectrics 280, the dummy gates 282, and the masks 284 may then bepatterned, for example, using photolithography and one or more etchprocesses, to form the interfacial dielectrics 280, the dummy gates 282,and the masks 284 for each gate structure 251.

The semiconductor device 240 also includes source/drain regions 292disposed in opposing regions of the fin 274 with respect to the gatestructures 251. The source/drain regions 292 and one of the gatestructures 251 (or the subsequently formed corresponding replacementgate structure) define at least a first transistor in a first transistorregion 201. The expression “source/drain” described in this disclosureis intended to refer to a source or drain region of a transistor, forexample the first transistor in the first transistor region 201. Thefirst transistor in the first transistor region 201 can be, for example,a pull-up transistor, such as the pull-up transistor 112 of FIG. 1B. Theother of the gate structures 251 (or the subsequently formedcorresponding replacement gate structure) is a portion of a secondtransistor in a second transistor region 203, and the second transistorcan be, for example, a pull-up transistor, such as the pull-uptransistor 116 of FIG. 1B. FIG. 2 further illustrates a referencecross-section that is used in later figures. Cross-section A-A is in aplane along, e.g., channels in the fin 274 between opposing source/drainregions 292. Subsequent figures refer to this reference cross-sectionfor clarity.

FIG. 3 illustrates the formation of gate spacers 286 along sidewalls ofthe gate structures 251 (e.g., sidewalls of the interfacial dielectrics280, dummy gates 282, and masks 284) and over the fin 274. The gatespacers 286 may be formed by conformally depositing one or more layersfor the gate spacers 286 and anisotropically etching the one or morelayers, for example. The one or more layers for the gate spacers 286 mayinclude a material different from the material(s) for the gate structure251. In some embodiments, the gate spacer 286 may include or be adielectric material, such as silicon oxygen carbide, silicon nitride,silicon oxynitride, silicon carbon nitride, the like, multi-layersthereof, or a combination thereof, and may be deposited by any suitabledeposition technique. An anisotropic etching process is then performedto remove portions of the spacer layers to form the gate spacers 286.

FIG. 4 illustrates the formation of epitaxial source/drain regions 292in recesses in the fin 274. The recesses are then formed in the fin 274on opposing sides of the gate structures 251. The recessing can be madeby an etch process. The etch process can be isotropic or anisotropic, orfurther, may be selective with respect to one or more crystalline planesof the substrate 270. Hence, the recesses can have variouscross-sectional profiles based on the etch process implemented.

Epitaxial source/drain regions 292 are epitaxially grown in therecesses. Depending on the conductivity type of the transistor, thematerial for the epitaxially source/drain regions 292 may be chosen toinclude or be silicon germanium, silicon carbide, silicon phosphorus,silicon carbon phosphorus, germanium, a III-V compound semiconductor, aII-VI compound semiconductor, or the like. The epitaxial source/drainregions 292 may be raised with respect to the fin 274 and may havefacets, which may correspond to crystalline planes of the semiconductorsubstrate 270 and the orientation of the fin 274 relative to thecrystalline plane of the substrate. In some examples, the epitaxialsource/drain regions 292 may also be doped, such as by in situ dopingduring epitaxial growth and/or by implanting dopants into the epitaxialsource/drain regions 28 after epitaxial growth.

FIG. 5 illustrates the formation and subsequent planarization of a firstinterlayer dielectric (ILD) 297. The first ILD 297 is formed over theexposed surfaces of the source/drain regions 292, sidewalls and topsurfaces of the gate spacers 286, top surfaces of the masks 284, and topsurfaces of the isolation regions 278 using any suitable depositiontechnique. An optional contact etch stop layer (CESL) (not shown) may bedeposited between the first ILD 297 and surfaces of the source/drain 292and sidewalls of the gate spacers 286. The first ILD 297 may include orbe tetraethylorthosilicate (TEOS) oxide, silicon dioxide, a low-kdielectric material (e.g., a material having a dielectric constant lowerthan silicon dioxide), or the like. The CESL may include or be siliconnitride, silicon carbon nitride, carbon nitride, the like, or acombination thereof. A planarization process, such as a chemicalmechanical planarization (CMP), may then remove the first ILD 297 untiltop surfaces of the dummy gates 282 are exposed, which may also removethe masks 284.

FIG. 6 illustrates the removal of the remaining gate structures 251 andthe formation of replacement gate structures 228 a, 228 b. The gatestructures 251 are removed using one or more etch processes. Uponremoval of the gate structures 251, recesses are formed between the gatespacers 286 where the gate stacks are removed, and channel regions ofthe fin 274 are exposed through the recesses. The replacement gatestructures 228 a, 228 b are then formed in the recesses where the gatestructures 251 were removed. The replacement gate structures 228 a, 228b each may include an interfacial dielectric 220, a gate dielectriclayer 222, one or more optional conformal layers 224, and a gateconductive fill material 226. The replacement gate structures 228 a, 228b may have a thickness in a range of about 8 nm to about 25 nm, forexample about 12 nm to about 20 nm.

The interfacial dielectric 220 is formed on top surfaces of the fin 274along the channel regions. The interfacial dielectric 220 can be anoxide (e.g., silicon oxide) formed by thermal or chemical oxidation ofthe fin 274.

The gate dielectric layer 222 can be conformally deposited in therecesses where gate stacks were removed (e.g., on the interfacialdielectric 220, and sidewalls of the gate spacers 286) and on the topsurfaces of the first ILD 297 and gate spacers 286. The gate dielectriclayer 222 can be or include silicon oxide, silicon nitride, a high-kdielectric material, multilayers thereof, or other dielectric material.A high-k dielectric material may have a k value greater than about 7.0,and may include a metal oxide of or a metal silicate of hafnium (Hf),aluminum (Al), zirconium (Zr), lanthanum (La), magnesium (Mg), barium(Ba), titanium (Ti), lead (Pb), multilayers thereof, or a combinationthereof.

The one or more optional conformal layers 224 can be conformallydeposited on the gate dielectric layer 222. The one or more optionalconformal layers 224 can include one or more barrier and/or cappinglayers and one or more work-function tuning layers. The one or morebarrier and/or capping layers can include tantalum nitride, titaniumnitride, the like, or a combination thereof. The one or morework-function tuning layer may include or be aluminum titanium carbide,aluminum titanium oxide, aluminum titanium nitride, the like, or acombination thereof. The materials for the one or more work-functiontuning layer, the barrier layer, and/or capping layer are selected sothat a desired threshold voltage (Vt) is achieved for the transistor,which could be a p-type field effect transistor (pFET) or an n-typefield effect transistor (nFET). The gate conductive fill material 226 isformed over the one or more conformal layers 224, if implemented, and/orthe gate dielectric layer 222. The gate conductive fill material 226 canfill remaining recesses where the gate stacks were removed. The gateconductive fill material 226 may be or include a metal-containingmaterial such as tungsten, cobalt, aluminum, ruthenium, copper,multi-layers thereof, a combination thereof, or the like.

A planarization process, like a CMP, may remove portions of the layerfor the gate conductive fill material 226, one or more conformal layers224, and gate dielectric layer 222 above the top surfaces of the firstILD 297 and gate spacers 286. The replacement gate structures 228 a, 228b including the gate conductive fill material 226, one or more conformallayers 224, gate dielectric layer 222, and interfacial dielectric 220may therefore be formed as illustrated in FIG. 6.

FIG. 7 illustrates the formation of a first self-aligned contact (SAC)231 on each of the replacement gate structures 228 a, 228 b and theformation of conductive features to the epitaxial source/drain regions292. After the formation of the replacement gate structures 228 a, 228b, respective portions of the replacement gate structures 228 a, 228 b,such as the top portions of the gate dielectric layer 222, the one ormore conformal layers 224, and the gate conductive fill material 226,are removed using one or more etch processes. Upon removal of the topportion of the replacement gate structures 228 a, 228 b, recesses areformed between the gate spacers 286. Respective first SACs 231 are thenformed in the recesses where the top portions of the gate dielectriclayer 222, the one or more conformal layers 224, and the gate conductivefill material 226 were removed. The first SAC 231 protects thereplacement gate structures 228 a, 228 b during subsequent formation ofopenings, which are configured to respectively accommodate subsequentbutted contacts for electrically connecting to the source/drain regions292. The first SAC 231 may include or be an insulating material, such assilicon oxide, silicon nitride, silicon oxynitride, silicon carbonoxynitride, silicon carbon nitride, any suitable dielectric material, orany combination thereof. In some embodiments, the first SAC 231 issilicon carbon oxynitride. The first SAC 231 may be formed by a CVD,PVD, ALD, any suitable deposition technique, or a combination thereof,and subsequent planarization, such as a CMP.

After the first SACs 231 are formed, source/drain contact openings areformed through the first ILD 297 to the source/drain regions 292 toexpose at least portions of the source/drain regions 292. Conductivefeatures are then formed in the source/drain contact openings. Theconductive features may include a silicide region 214 formed on thesource/drain regions 292 and a conductive material 246 formed over thesilicide region 214. The first ILD 297 may be patterned with theopenings, for example, using photolithography and one or more etchprocesses, such as a dry etch or any suitable anisotropic etch process.While not shown, each conductive material 246 may include, for example,an adhesion layer conformally deposited in the source/drain contactopenings and over the first ILD 297, a barrier layer conformallydeposited on the adhesion layer, and a conductive fill materialdeposited on the barrier layer. The silicide region 214 may be formed bythermally reacting an upper portion of the source/drain regions 292 withthe adhesion layer, which can be titanium, tantalum, or the like. Thebarrier layer may be or include titanium nitride, titanium oxide,tantalum nitride, tantalum oxide, any suitable transition metal nitridesor oxides, the like, or any combination thereof. The conductive fillmaterial may be or include cobalt, tungsten, copper, ruthenium,aluminum, gold, silver, alloys thereof, the like, or a combinationthereof. After the conductive fill material is deposited, excessconductive fill material, barrier layer, and adhesion layer may beremoved by using a planarization process, such as a CMP, for example.Hence, top surfaces of the conductive material 246 and the first ILD 297may be coplanar.

FIG. 8 illustrates etching back the conductive material 246 to therebyform recesses 248. The etch back can include using one or more etchprocesses selective to the conductive material 246. The recesses 248 areformed so that the top surface of the conductive material 246 is lowerthan the top surfaces of the first ILD 297, the first SAC 231 and thegate spacers 286.

FIG. 9 illustrates forming a protective liner 250. After the recesses248 are formed, the protective liner 250 is conformally deposited in therecesses 248 (e.g., on the exposed surfaces of the first ILD 297 and theconductive material 246) and on the top surfaces of the first ILD 297,the first SAC 231, and the gate spacers 286. The protective liner 250may prevent damage to underlying device features during etching ofcontact openings. In some embodiments, the protective liner 250 may beformed of a material having a relatively high etch selectivity comparedto the gate spacers 286. For example, the protective liner 250 may be adielectric which may include or be aluminum oxide (AlO_(x)), aluminumoxynitride (AlON), aluminum nitride (AlN), titanium oxide (TiO_(x)),titanium oxynitride (TiON), titanium nitride (TiN), and the like. In anexample, the protective liner 250 is AlON. The protective liner 250 maybe deposited by ALD, PVD, CVD, or any suitable deposition technique.

FIG. 10 illustrates forming a second SAC 233. After the protective liner250 is formed, the second SAC 233 is formed over the protective liner250. The second SAC 233 may be formed of a material different from thefirst SAC 231. The second SAC 233 may be made of an insulating material,such as silicon oxide, silicon nitride, silicon oxynitride, siliconcarbon oxynitride, silicon carbon nitride, any suitable dielectricmaterial or any combination thereof. In some embodiments, the second SAC233 is silicon nitride. The second SAC 233 may be formed by a CVD, PVD,any suitable deposition technique, or a combination thereof. If desired,a planarization process, like a CMP, may be used to planarize the topsurface of the second SAC 233.

FIG. 10 further illustrates the formation of a first hard mask layer235, a second hard mask layer 237, and a tri-layer mask structure 239sequentially over the second SAC 233. The first hard mask layer 235 andthe second hard mask layer 237 are configured to provide etchingselectivity relative to the second SAC 233 and the first hard mask layer235, respectively, during one or more etch processes. The first hardmask layer 235 may be made of a metal compound, such as titanium nitride(TiN), tungsten carbide (WC), tantalum nitride (TaN), tungsten nitride(WN), or another material. The second hard mask layer 237 may include orbe a silicon oxide layer or any suitable oxide materials. The first hardmask layer 235 and second hard mask layer 237 may be deposited by anysuitable deposition technique, such as PVD, CVD, or the like. Thetri-layer mask structure 239 includes a bottom layer 241, a middle layer243, and a top layer 245. The tri-layer structure 239 may be selected tobe suitable for a deep ultraviolet (DUV) or an extreme ultraviolet (EUV)photolithography. The bottom layer 241 may be a bottom anti-reflectivecoating (BARC) layer, such as silicon rich oxide or silicon oxycarbide(SiOC). The middle layer 243 may be a silicon-containing ormetal-containing polymer. The top layer 245 may be a radiation sensitivelayer, such as a photoresist. The bottom layer 241, middle layer 243,and top layer 245 may be deposited by any suitable deposition technique,such as PVD, CVD, spin-on coating, or the like.

FIG. 11 illustrates the formation of a first opening 247 through the toplayer 245 and middle layer 243 of the tri-layer mask structure 239during a first photolithography and etch process. The first opening 247formed in the top layer 245 is generally aligned with the replacementgate 228 b. The first photolithography process is performed bypositioning a first photomask 249 over the structure of FIG. 10. Thefirst photomask 249 may be suitable for exposure with DUV radiation suchas ArF excimer laser (193 nm) or KrF excimer laser (248 nm). The firstphotomask 249 has a first pattern 255 which can be various features suchas squares, lines, holes, grids, or any desired shape such as polygons,depending on the features to be formed in a target layer. In someembodiments, the first pattern 255 contains a square pattern.

Inset 289 in FIG. 11 is an enlarged top view of a portion of a pattern291 of the first photomask 249 used to pattern the top layer 245according to some embodiments. The pattern 291 includes a plurality offeatures 293 a, 293 b, 293 c, 293 d, which can be lines, squares, grids,or any desired shape such as polygons, depending on the features to beformed in the top layer 245. In some embodiments, the features 293 a,293 b, 293 c, 293 d are a square-shape pattern. It is contemplated thatfour features and their arrangement are shown for illustrative purposes.The features 293 a, 293 b, 293 c, 293 d can be repetitive on the firstphotomask 249, depending on the application and the features to beformed in the semiconductor device 240. The features 293 a, 293 b, 293c, 293 d may be to provide openings for contacts that provide electricalconnection to source/drain regions and/or gate for the semiconductordevice 240. For example, the feature 293 a may be a square-shape patterncorresponding to a portion of a first butted contact (e.g., the pattern158A of the butted contact 158, as shown in FIG. 1B). The feature 293 bmay be a square-shape pattern corresponding to a portion of a secondbutted contact (e.g., the pattern 159A of the butted contact 159, asshown in FIG. 1B). The features 293 c, 293 d may be a square-shapepattern corresponding to contact features (e.g., the contact patterns162A as shown in FIG. 1B). The features 293 a, 293 b of the firstphotomask 249 and features 279 a, 279 b from a second photomask 269 (tobe discussed below in FIG. 14) are recombined to produce arectangular-shape butted contact (e.g., butted contacts 158, 159 asshown in FIG. 1B) which is to be transferred to a target layer (e.g.,the second SAC 233). Depending on the application, the features 293 a,293 b, 293 c, 293 d may have a dimension in a range between about 10 nmand about 80 nm, for example about 20 nm to about 55 nm.

The first pattern 255 is transferred to the top layer 245 by exposingthe top layer 245 to a radiation beam 257 using the first photomask 249.The radiation beam 257 may be a EUV radiation (e.g., 13.5 nm) or a DUVradiation such as ArF excimer laser (193 nm) or KrF excimer laser (248nm). Depending on the mask material, other suitable radiations, such asan e-beam, an x-ray, or an ion beam, may also be used. Exposed orunexposed portions of the top layer 245 may then be removed depending onwhether a positive or negative resist is used.

The middle layer 243 is then patterned using the patterned top layer 245as a mask. As a result, the first opening 247 of the top layer 245 istransferred to the middle layer 243. The middle layer 243 may bepatterned using any suitable process, such as a dry etch process.Example dry etch process may be performed in a dual RF power sourceplasma reactor using a chemistry containing an inert gas, such as argon,and a fluorocarbon gas such as tetrafluoromethane (CF₄),trifluoromethane (CHF₃), hexafluorobutadiene (C₄F₆), difluoromethane(CH₂F₂), octofluoropropane (C₃F₈), octofluorocyclobutane (C₄F₈), or anycombinations thereof. In some embodiments, the chemistry includes CF₄and CHF₃. The plasma reactor may be maintained at a chamber pressure ofabout 5 mTorr to about 20 mTorr, for example about 10 mTorr. During thedry etch process, the source power is provided at a first power leveland the bias power is provided at a second power level, and a ratio ofthe first power level to the second power level may be controlled in arange between about 30:1 and about 10:1, for example about 20:1. In someembodiments, the first power is about 300 W and the second power isabout 15 W, for example.

FIG. 12 illustrates the formation of the first opening 247 through thebottom layer 241 and the underlying hard mask layers 235 and 237. Thebottom layer 241 is patterned using the patterned top and middle layers245, 243 as a mask. The bottom layer 241 may be patterned using anysuitable process, such as a dry etch process. The dry etch process maybe performed in the dual RF power source plasma reactor. Example dryetch process for etching the bottom layer 241 may include a first etchprocess and a second etch process following the first etch process. Dueto the shrunken device feature sizes, the margin for a misalignmentbetween the contact openings and the gate electrode is significantlyreduced in advanced technology. A reduced margin for misalignment maycause substantial device yield loss or create serious device reliabilityconcerns, especially in a butted contact area, where a misalignment mayeasily cause a complete disconnection to a source/drain region or a gateelectrode. Therefore, it may be advantageous to form the first opening247 with a wider diameter for ease of lithography process, and thentailor/decrease the diameter of the opening when transferring throughthe tri-layer structure 239. The two-stage etch process allows gradualreduction of the pattern critical dimension in the bottom layer 241. Thereduced pattern critical dimension can avoid the chances of misalignmentbetween the contact opening and the gate electrode.

In some embodiments, the first etch process uses a first chemistrycontaining N₂ and H₂. The N₂ is flowed into the plasma reactor at afirst volumetric flowrate, and the H₂ is flowed into the plasma reactorat a second volumetric flowrate, and a ratio of the first volumetricflowrate to the second volumetric flowrate can be controlled in a rangefrom about 2:1 and about 5:1, for example about 3:1. The plasma reactormay be maintained at a chamber pressure of about 1 mTorr to about 30mTorr, for example about 10 mTorr. During the first etch process, thesource power is provided at a first power level and the bias power isprovided at a second power level, and a ratio of the first power levelto the second power level may be controlled in a range between about 3:1and about 7:1, for example about 5:1. In some embodiments, the firstpower is about 500 W and the second power is about 100 W, for example.

After the first etch process, the second etch process is performed inthe same plasma reactor using a second chemistry containing carbondioxide (CO₂) and oxygen (O₂). The CO₂ is flowed into the plasma reactorat a first volumetric flowrate, and the O₂ is flowed into the plasmareactor at a second volumetric flowrate, and a ratio of the firstvolumetric flowrate to the second volumetric flowrate can be controlledin a range from about 2:1 and about 6:1, for example about 3:1. Theplasma reactor may be maintained at a chamber pressure of about 1 mTorrto about 30 mTorr, for example about 10 mTorr. During the second etchprocess, the source power is provided at a first power level and thebias power is provided at a second power level, and a ratio of the firstpower level to the second power level may be controlled in a rangebetween about 2:1 and about 6:1, for example about 4:1. In someembodiments, the first power is about 200 W and the second power isabout 50 W, for example. Upon completion of the second etch process, theopening of the top layer 245 may have a first diameter and the openingof the bottom layer 241 may have a second diameter relatively smallerthan the first diameter.

The second hard mask layer 237 is then patterned using the patternedtri-layer structure 239 as a mask. The second hard mask layer 237 may bepatterned using any suitable process, such as a dry etch process. Thedry etch process may be performed in the dual RF power source plasmareactor. Example dry etch process for etching the second hard mask layer237 may include using a chemistry containing an inert gas, such asargon, and a fluorocarbon gas such as CF₄, CHF₃, C₄F₆, hexafluoroethane(C₂F₆), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈),octofluorocyclobutane (C₄F₈), or any combination thereof. In someembodiments, the chemistry includes CF₄ and argon. The plasma reactormay be maintained at a chamber pressure of about 5 mTorr to about 20mTorr, for example about 10 mTorr. During the dry etch process, thesource power is provided at a first power level and the bias power isprovided at a second power level, and a ratio of the first power levelto the second power level may be controlled in a range between about 2:1and about 6:1, for example about 3.5:1. In some embodiments, the firstpower is about 500 W and the second power is about 150 W, for example.

Thereafter, a dry etching process and/or a strip process, such as anashing process, may be performed to sequentially remove the patternedtop layer 245, the patterned middle layer 243, and the patterned bottomlayer 241. A wet cleaning process may be performed following the stripprocess.

An etch process is then performed to transfer the first opening 247 fromthe second hard mask 237 to the first hard mask layer 235. The etchprocess may be a dry etch process performed in the dual RF power sourceplasma reactor. Example dry etch process for etching the first hard masklayer 235 may include using a chemistry containing an inert gas, such asargon, and a fluorocarbon gas such as CF₄, CHF₃, C₄F₆, hexafluoroethane(C₂F₆), difluoromethane (CH₂F₂), octofluoropropane (C₃F₈),octofluorocyclobutane (C₄F₈), or any combination thereof. In someembodiments, the chemistry includes C₄F₈ and argon. The plasma reactormay be maintained at a chamber pressure of about 5 mTorr to about 20mTorr, for example about 10 mTorr. During the dry etch process, thesource power is provided at a first power level and the bias power isprovided at a second power level, and a ratio of the first power levelto the second power level may be controlled in a range between about 2:1and about 6:1, for example about 4:1. In some embodiments, the firstpower is about 200 W and the second power is about 50 W, for example. Awet cleaning process may be performed following the dry etch process toremove residues.

FIG. 13 illustrate the formation of a first contact opening 259 throughportions of the second SAC 233, the protective liner 250, the first SAC231, and the gate spacers 286, using the patterned second hard mask 237and the patterned first hard mask layer 235 as a mask. The first contactopening 259 can be formed by using one or more etch processes. Exampleetch processes may include a first dry etch process performed in thedual RF power source plasma reactor to remove a portion of the secondSAC 233 using the patterned second hard mask 237 and the patterned firsthard mask layer 235 as a mask. The first dry etch process may use achemistry including a fluorine-containing gas and an inert gas such asargon. Suitable fluorine-containing gas may include, but is not limitedto CF₄, CHF₃, CH₃F, C₄F₆, C₂F₆, CH₂F₂, C₄F₈, or any combination thereof.In some embodiments, the chemistry includes C₄F₈ and CH₃F. Thefluorine-containing gas is flowed into the plasma reactor at a firstvolumetric flowrate, and the argon is flowed into the plasma reactor ata second volumetric flowrate, and a ratio of the first volumetricflowrate to the second volumetric flowrate can be controlled in a rangefrom about 1:1 and about 3:1, for example about 2:1. The plasma reactormay be maintained at a chamber pressure of about 5 mTorr to about 200mTorr, for example about 10 to 50 mTorr. During the dry etch process,the source power is provided at a first power level and the bias poweris provided at a second power level, and a ratio of the first powerlevel to the second power level may be controlled in a range betweenabout 1:1 and about 2:1. In some embodiments, the first power is about300 to 500 W and the second power is about 100 W, for example.

Upon removal of the second SAC 233, a portion of the protective liner250 is exposed. A second dry etch process may then be performed in thedual RF power source plasma reactor to remove the exposed protectiveliner 250, using the patterned second hard mask 237 and the patternedfirst hard mask layer 235 as a mask. The second dry etch process may usea chemistry including a chlorine-containing gas and an inert gas such ashelium or argon. Suitable chlorine-containing gas may include, but isnot limited to chlorine (Cl₂) and boron trichloride (BCl₃), methylfluoride (CH₃F), and the like. The plasma reactor may be maintained at achamber pressure of about 10 mTorr to about 300 mTorr, for example about100 mTorr. During the second dry etch process, the source power isprovided at a first power level and the bias power is provided at asecond power level, and a ratio of the first power level to the secondpower level may be controlled in a range between about 3:1 and about6:1, for example about 5:1. In some embodiments, the first power isabout 800 W and the second power is about 150 W, for example.

Upon removal of the protective liner 250, a portion of the first SAC 231and a portion of the gate spacers 286 are exposed. A third dry etchprocess may be performed in the dual RF power source plasma reactor toremove the exposed first SAC 231, using the patterned second hard mask237 and the patterned first hard mask layer 235 as a mask. In somecases, removing the exposed first SAC 231 may be performed using thegate spacers 286 as a mask. In any case, top surfaces of the gatespacers 286, the gate dielectric layer 222, the one or more optionalconformal layers 224, and the gate conductive fill material 226 areexposed as a result of the third dry etch process. The third dry etchprocess may use a chemistry including a fluorine-containing gas and ahydrogen-containing gas. Suitable fluorine-containing gas may include,but is not limited to F₂, CF₄, CHF₃, C₄F₆, C₂F₆, CH₂F₂, C₄F₈, SF₆, orany combination thereof. Suitable hydrogen-containing gas may include,but is not limited to CH₄, H₂, NH₃, a hydrocarbon or any molecule withan abstractable hydrogen atom, or any combination thereof. The chemistrymay further include an oxygen-containing gas, such as O₂, NO, N₂O etc.In some embodiments, the chemistry includes CF₄ and CH₄. The plasmareactor may be maintained at a chamber pressure of about 5 mTorr toabout 200 mTorr, for example about 50 mTorr. During the dry etchprocess, the source power is provided at a first power level and thebias power is provided at a second power level, and a ratio of the firstpower level to the second power level may be controlled in a rangebetween about 2:1 and about 6:1, for example about 4:1. In someembodiments, the first power is about 1600 W and the second power isabout 350 W, for example.

The first contact opening 259 has a bottom 215 and a sidewall 217extending upwardly from the bottom 215. The bottom 215 can besubstantially co-planar with the top surfaces of the gate conductivefill material 226, the gate dielectric layer 222, and one or moreoptional conformal layers 224. In some embodiments, the bottom 215 mayfurther extend into a portion of the gate spacers 286. The sidewall 217may be at an angle “A” with respect to the bottom 215. In someembodiments, the angle “A” is in a range between 91° to about 100°, suchas about 92° to about 95°, for example about 93° to about 94°. The angle“A” may vary depending upon the application and/or the parameters usedby the etch process(es) during the formation of the first contactopening 259.

FIG. 14 illustrates the formation of a tri-layer structure 261 over thestructure of FIG. 13. The tri-layer structure 261, which can implementthe same or similar materials using the same or similar processes as thetri-layer structure 239, includes a bottom layer 263, a middle layer265, and a top layer 267. The first contact opening 259 is filled andoverburdened by the bottom layer 263 to a predetermined thickness. In anexample, the top surface of the bottom layer 263 is higher than the topsurface of the second hard mask layer 237. The middle layer 265 and thetop layer 267 are then sequentially deposited over the bottom layer 263.

After the tri-layer structure 261 is formed, the top layer 267 ispatterned using a second photolithography process. The secondphotolithography process is performed by positioning a second photomask269 over the semiconductor device 240. The second photomask 269 has asecond pattern 271. The second pattern 271 may have features similar tothe first pattern 255 as discussed above. In some embodiments, thesecond pattern 271 contains a square pattern. Likewise, the secondpattern 271 can be transferred to the top layer 267 via exposure to aradiation beam 257 with the exposed portion of the top layer 267 beingremoved. As a result, a second opening 273 is formed in the top layer267. The second opening 273 formed in the top layer 267 is generallyaligned with the source/drain region 292, as shown in FIG. 14. Thesecond opening 273 may have a width similar, greater or smaller than thewidth of the first opening 247, depending upon the application.

Inset 275 in FIG. 14 is an enlarged top view of a portion of a pattern277 of the second photomask 269 used to pattern the top layer 267according to some embodiments. The second photomask 269 may be suitablefor exposure with DUV radiation such as ArF excimer laser (193 nm) orKrF excimer laser (248 nm). The pattern 277 includes a plurality offeatures 279 a, 279 b, 279 c, 279 d, which can be lines, squares, grids,or any desired shape such as polygons, depending on the features to beformed in the top layer 267. In some embodiments, the features 279 a,279 b, 279 c, 279 d are a square-shape pattern. It is contemplated thatfour features and their arrangement are shown for illustrative purposes.The features 279 a, 279 b, 279 c, 279 d can be repetitive on the secondphotomask 269, depending on the application and the features to beformed in the semiconductor device 240. The features 279 a, 279 b, 279c, 279 d may be to provide openings for contacts that provide electricalconnection to source/drain regions and/or gate for the semiconductordevice 240. For example, the feature 279 a may be a square-shape patterncorresponding to a portion of a first butted contact (e.g., the pattern158B of the butted contact 158, as shown in FIG. 1B). The feature 279 bmay be a square-shape pattern corresponding to a portion of a secondbutted contact (e.g., the pattern 159B of the butted contact 159, asshown in FIG. 1B). The features 279 c, 279 d may be a square-shapepattern corresponding to contact features (e.g., the contact pattern160A as shown in FIG. 1B). The features 279 a, 279 b of the secondphotomask 269 and the features 293 a, 293 b from the first photomask 249are recombined to produce a rectangular-shape butted contact (e.g.,butted contacts 158, 159 as shown in FIG. 1B) which is to be transferredto a target layer (e.g., the second SAC 233). By breaking a layout intomultiple different masks, (e.g., first photomask 249 and the secondphotomask 269), features can be formed separately on a single layerusing multiple masks in succession. Therefore, a minimum line spacing inthe combined pattern can be reduced while maintaining good resolution.

It should be understood that the features 293 a, 293 b, 293 c, 293 d andthe features 279 a, 279 b, 279 c, 279 d discussed in this disclosure canbe any shape and/or arranged in any desired configuration of patterns solong as the combination of the features 293 a, 293 b, 293 c, 293 d andthe features 279 a, 279 b, 279 c, 279 d produce a pre-determined,completed shape of the butted contacts and/or other contact featuresdesired in the semiconductor device 240.

After the top layer 267 is patterned, the middle layer 265 and thebottom layer 263 can be patterned in a similar fashion as discussedabove with respect to FIGS. 11 and 12 using the patterned top layer 267as a mask, thereby transferring the second opening 273 to the bottomlayer 263. Thereafter, the second hard mask layer 237 can be patternedin a similar fashion as discussed above with respect to FIGS. 11 and 12using the patterned structure 261 as a mask. The bottom layer 263 in thefirst contact opening 259 remains at this stage. Then, an etch processcan be performed to transfer the modified second opening 273 from thesecond hard mask layer 237 to the first hard mask layer 235 in a similarfashion as discussed above with respect to FIG. 12.

FIG. 15 illustrates the formation of a second contact opening 281through the second SAC 233 and the protective liner 250. One or moreetch processes are then performed to remove portions of the second SAC233 and the protective liner 250 using the patterned second hard mask237, the patterned first hard mask layer 235 (and in some case remainingportion of the bottom layer 263 in the first contact opening 259) as amask, thereby forming the second contact opening 281 with an angledprofile. The second contact opening 281 exposes at least the top surfaceof the conductive material 246. A first etch process, such as the firstdry etch process used for removing the second SAC 233 as discussed abovewith respect to FIG. 13, may be used to remove the second SAC 233. Asecond etch process, such as the second dry etch process used forremoving the protective liner 250 as discussed above with respect toFIG. 13, may be used to remove the protective liner 250. The bottomlayer 263 remaining in the first contact opening 259 can be removedafter the etch processes using a suitable strip process, such as anashing process.

The second contact opening 281 has a bottom 223 and a sidewall 225extending upwardly from the bottom 223. The sidewall 225 may be at anangle “B” with respect to the bottom 223. In some embodiments, the angle“B” is in a range between 91° to about 100°, such as about 92° to about95°, for example about 93° to about 94°. The angle “B” may varydepending upon the parameters used by the etch process(es) during theformation of the second contact opening 281.

FIG. 15 depicts the first contact opening 259 and the second contactopening 281. The first contact opening 259 and the second contactopening 281 together expose portions of the conductive material 246, thefirst ILD 297, the gate conductive fill material 226, the gatedielectric layer 222, one or more optional conformal layers 224, and thegate spacers 286. The combination of the first contact opening 259 andthe second contact opening 281 provide a contact opening for a buttedcontact, such as the butted contacts 158 and 159 as shown in FIG. 1B.Particularly, the gate spacer 286 left between the replacement gatestructure 228 b and the source/drain region 292 is formed with a taperedtop portion 286′ due to the angled sidewalls of the first and secondcontact openings 259, 281.

FIG. 16 illustrates filling the first and second contact openings 259,281 (collectively referred to as a butted contact opening 238) with aconductive fill 227 (e.g., contact metal). The conductive fill 227 maybe or include tungsten, cobalt, copper, ruthenium, aluminum, gold,silver, alloys thereof, the like, or a combination thereof, and may bedeposited by PVD, ECP, ALD, CVD, or any suitable deposition technique.In some cases, a barrier/adhesion layer (not shown) may be conformallydeposited on exposed surfaces of the butted contact opening 238. Thebarrier/adhesion layer may include or be titanium nitride,titanium-silicon nitride, titanium-carbon nitride, titanium-aluminumnitride, tantalum nitride, tantalum-silicon nitride, tantalum-carbonnitride, tungsten nitride, tungsten carbide, tungsten-carbon nitride,the like, or a combination thereof, and may be deposited by ALD, PECVD,MBD, or any suitable deposition technique. After the conductive fill 227is deposited, excess conductive fill 227 may be removed by using aplanarization process, such as a CMP, for example. The planarizationprocess may remove excess conductive fill 227, the second hard masklayer 237, the first hard mask layer 235, and the second SAC 233 untilthe top surface 229 of the protective liner 250 is exposed. FIG. 17Aillustrates the top surface 229 of the protective liner 250, the topsurface 234 of the conductive fill 227, and the top surface 236 thesecond SAC 233 are substantially coplanar after the planarizationprocess. The butted contact opening 238 generally has a first bottom1702 extending across and over the source/drain region 292 and a secondbottom 1704 extending across and over the replacement gate structure 228b. A tapered feature (e.g., the tapered top portion 286′ of the gatespacer 286) is disposed between the first bottom 1702 and the secondbottom 1704 and extends upwardly from between the source/drain region292 and the replacement gate structure 228 b. While the first bottom1702 is shown higher than the second bottom 1704, the first bottom 1702may be at the same elevation as the second bottom 1704, or even lowerthan the second bottom 1704, depending on the process receipts and/orapplication. FIG. 17B illustrates one embodiment where the first bottom1702 and the second bottom 1704 are at the same elevation. Theconductive fill 227 in the butted contact opening 238 enables electricalconnection between the conductive material 246 contacting thesource/drain region 292 and the gate conductive fill material 226 of thereplacement gate structure 228 b without the use of a horizontal metalinterconnect layer. As a result, a shared or butted contact, such as thebutted contacts 158 and 159 as shown in FIG. 1B, is obtained.

After the conductive fill 227 is formed in the butted contact opening238, the structure may undergo further processing to form variousfeatures and regions needed to complete a SRAM cell. For example,subsequent processing may form additional contacts/vias/lines andmultilayers of interconnect features (e.g., metal layers and interlayeror intermetal dielectrics) on the substrate 270, configured to connectthe various features to form a functional circuit that may include oneor more devices.

FIG. 18 depicts a portion of the cross-sectional view of FIG. 17A tofurther illustrate additional details in accordance with someembodiments. It should be understood that FIG. 18 is not drawn in scalefor ease of illustration purposes. The butted contact structure 1800 canbe considered as a W-shaped structure having a left V-shaped part 1802and a right V-shaped part 1804. The butted contact structure 1800 has afirst dimension D1 along a top surface 1801 of the butted contactstructure 1800. The left V-shaped part 1802 has a second dimension D2along the bottom 1702 of the left V-shaped part 1802. The right V-shapedpart 1804 has a third dimension D3 along the bottom 1704 of the rightV-shaped part 1804. The ratio of the second dimension D2 to the firstdimension D1 can be in a range from about 1:1.5 to about 1:3, and theratio of the third dimension D3 to the first dimension D1 can be in arange from about 1:1.5 to about 1:3. The bottom 1702 of the leftV-shaped part 1802 and the bottom 1704 of the right V-shaped part 1804may be non-coplanar. In the embodiment shown in FIG. 18, the bottom 1702of the left V-shaped part 1802 is relatively higher than the bottom 1704of the right V-shaped part 1804 by a fourth dimension D4. The fourthdimension D4 can be in a range from about −5 nm to about 5 nm. In otherwords, the bottom 1702 of the left V-shaped part 1802 may also be lowerthan the bottom 1704 of the right V-shaped part 1804. The left V-shapedpart 1802 has a fifth dimension D5 measuring from the top surface 1801to the bottom 1702 of the left V-shaped part 1802. The right V-shapedpart 1804 has a sixth dimension D6 measuring from the top surface 1801to the bottom 1704 of the right V-shaped part 1804. A ratio of the fifthdimension D5 to the sixth dimension D6 can be in a range from about0.9:1 to about 1.2:1, for example about 1:1.

The left V-shaped part 1802 has a sidewall 1814 extending between thetop surface 1801 of the butted contact structure 1800 and the bottom1702 of the left V-shaped part 1802. The right V-shaped part 1804 has asidewall 1816 extending between the top surface 1801 of the buttedcontact structure 1800 and the bottom 1704 of the right V-shaped part1804. A gate spacer 286 is disposed between the source/drain region 292and the replacement gate structure 228 b. The gate spacer 286 has atapered portion 286′ separating the left V-shaped part 1802 and theright V-shaped part 1804. In other words, the bottom 1702 of the leftV-shaped part 1802 and the bottom 1704 of the right V-shaped part 1804are not contiguous. The tapered portion 286′ has a first sidewall 1818and a second sidewall 1820 intersecting the first sidewall 1818 at anangle “E” that is greater than 0°, for example about 2° to about 20°.The first sidewall 1818 is at an angle “F” with respect to the bottom1704 of the right V-shaped part 1804. The second sidewall 1820 is at anangle “G” with respect to the bottom 1702 of the left V-shaped part1802. The angle “F” can be in a range from 91° to about 100°, forexample about 92° to about 95°. The angle “G” can be in a range from 91°to about 100°, for example about 92° to about 95°.

Various embodiments described herein may offer several advantages. Itwill be understood that not all advantages have been necessarilydescribed herein, no particular advantage is required for anyembodiment, and other embodiments may offer different advantages. As anexample, embodiments described herein provide an improved butted contactstructure that enables connection of one or more gates to one or moreactive regions without the use of a horizontal metal interconnect layer.The butted contact structure between gate contacts and source or draincontacts can all be formed by a double patterning process using twoseparate photomasks, each with half of a pattern corresponding to theshared or butted contact structure. By reducing the total number ofphotomasks to two, the number of alignments of photomasks is reduced,and reduction in yield caused by misalignment with another photomask issuppressed. As a result, manufacturing cost can be reduced andthroughput can be improved. In addition, the improved butted contactstructure has a tapered gate spacer extruding into a bottom of thebutted contact structure. The tapered gate spacer along with the angledsidewalls of the butted contact structure can ensure good metal-fillcapability for the subsequent deposited metal fill. Therefore, the metalfill can be fully deposited in the butted contact structure withoutvoids or seams.

In an embodiment, a structure is provided. The structure includes afirst transistor on a substrate, the first transistor comprising a firstsource or drain region, a first gate, and a first gate spacer beingdisposed between the first gate and the first source or drain region.The structure also includes a second transistor on the substrate, thesecond transistor comprising a second source or drain region, a secondgate, and a second gate spacer being disposed between the second gateand the second source or drain region. The structure further includes abutted contact disposed above and extending from the first source ordrain region to at least one of the first gate or the second gate, aportion of the first gate spacer extending a distance into the buttedcontact to separate a first bottom surface of the butted contact from asecond bottom surface of the butted contact.

In another embodiment, a structure includes a first transistor on asubstrate, the first transistor comprising a source or drain region, aconductive feature contacting the source or drain region, a gateelectrode of a gate structure of a second transistor on the substrate.The structure also includes a butted contact comprising (i) a firstsurface contacting the gate electrode, (ii) a second surface contactingthe conductive feature, (iii) a third surface extending at a first anglefrom the first surface, and (iv) a fourth surface extending at a secondangle from the second surface, the third surface intersecting the fourthsurface at a third angle. The structure further includes a gate spacerdisposed between the source or drain region and the gate structure, aportion of the gate spacer being disposed laterally between the thirdsurface and the fourth surface.

In one another embodiment, a method for semiconductor processing isprovided. The method includes forming a source or drain region of afirst transistor on a substrate, a gate of a second transistor on thesubstrate, and a gate spacer on a side of the gate, wherein the sourceor drain region has a conductive feature formed thereon, the gate has afirst dielectric layer formed thereon, and the gate spacer is disposedlaterally between the gate and the source or drain region, depositing asecond dielectric layer over the conductive feature, the firstdielectric layer, and the gate spacer, wherein the second dielectriclayer is different from the first dielectric layer, depositing a firstmask layer over the second dielectric layer, depositing a second masklayer over the first mask layer, etching a first contact opening throughthe second mask layer, the first mask layer, the second dielectriclayer, and the first dielectric layer to expose the gate, etching thefirst contact opening comprising using a first etch recipe to etch thesecond dielectric layer, and a fourth etch recipe to etch the firstdielectric layer, wherein the first, second, third, and fourth etchrecipes are different from each other, etching a second contact openingthrough the second mask layer, the first mask layer, and the seconddielectric layer to expose the conductive feature, etching the secondcontact opening comprising using the first etch recipe to etch thesecond mask layer, the second etch recipe to etch the first mask layer,the third etch recipe to etch the second dielectric layer, the firstcontact opening and the second contact opening joining at the gatespacer, and the first etch recipe and the second etch recipe shaping aportion of the gate spacer into a tapered profile, and filling the firstcontact opening and the second contact opening with a conductivematerial.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A structure comprising: a first transistor on asubstrate, the first transistor comprising a first source or drainregion, a first gate, and a first gate spacer being disposed between thefirst gate and the first source or drain region; a second transistor onthe substrate, the second transistor comprising a second source or drainregion, a second gate, and a second gate spacer being disposed betweenthe second gate and the second source or drain region; and a buttedcontact disposed above and extending from the first source or drainregion to at least one of the first gate or the second gate, a portionof the first gate spacer extending a distance into the butted contact toseparate a first bottom surface of the butted contact from a secondbottom surface of the butted contact.
 2. The structure of claim 1,wherein the portion of the first gate spacer has a tapered profile. 3.The structure of claim 1, wherein the portion of the first gate spacerhas a first sidewall and a second sidewall intersecting the firstsidewall.
 4. The structure of claim 3, wherein the first sidewallcontacts the first bottom surface of the butted contact at an angle in arange of 91° to 100°.
 5. The structure of claim 3, wherein the firstbottom surface and the second bottom surface are at a same elevation. 6.The structure of claim 3, wherein the first bottom surface and thesecond bottom surface are at different elevations.
 7. The structure ofclaim 1, wherein a ratio of a width of the butted contact at the firstsource or drain region to a width of the butted contact along an uppersurface of the butted contact is in a range from about 1:1.5 to about1:3.
 8. A structure comprising: a first transistor on a substrate, thefirst transistor comprising a source or drain region; a conductivefeature contacting the source or drain region; a gate electrode of agate structure of a second transistor on the substrate; a butted contactcomprising (i) a first surface contacting the gate electrode, (ii) asecond surface contacting the conductive feature, (iii) a third surfaceextending at a first angle from the first surface, and (iv) a fourthsurface extending at a second angle from the second surface, the thirdsurface intersecting the fourth surface at a third angle; and a gatespacer disposed between the source or drain region and the gatestructure, a portion of the gate spacer being disposed laterally betweenthe third surface and the fourth surface.
 9. The structure of claim 8,wherein the first surface and the second surface are co-planar.
 10. Thestructure of claim 8, wherein the first surface and the second surfaceare at different elevations.
 11. The structure of claim 8, wherein thefirst angle is in a range from 91° to 100°, the second angle is in arange from 91° to 100°, and the third angle is greater than 0°.
 12. Thestructure of claim 8, wherein the portion of the gate spacer has atapered profile.
 13. The structure of claim 8, wherein the buttedcontact comprises tungsten, cobalt, copper, ruthenium, aluminum, gold,silver, an alloy thereof, or a combination thereof.
 14. The structure ofclaim 8, wherein a vertical distance between the first surface and thesecond surface is less than about 5 nm.
 15. A structure comprising: anactive area in a substrate; a conductive feature over the active area; agate structure over the substrate, the gate structure comprising a gatespacer and a gate electrode, wherein the gate spacer is interposedbetween the gate electrode and the conductive feature; and a buttedcontact contacting the conductive feature and the gate electrode,wherein an upper surface of the gate spacer is higher than a firstinterface between the gate electrode and the butted contact, wherein theupper surface of the gate spacer is higher than a second interfacebetween the conductive feature and the butted contact.
 16. The structureof claim 15, wherein the gate spacer has angled sidewalls that intersectat an angle between about 2° to about 20°.
 17. The structure of claim 15further comprising a silicide region interposed between the conductivefeature and the active area.
 18. The structure of claim 15 furthercomprising an interlayer dielectric layer over the substrate, wherein afirst portion of the interlayer dielectric layer is interposed betweenthe gate spacer and the conductive feature.
 19. The structure of claim18, wherein the gate spacer protrudes above the first portion of theinterlayer dielectric layer.
 20. The structure of claim 15, wherein thefirst interface is non-planar with the second interface.